part of my USAF job required me to occasionally schlep 1:250,000 aeronautical charts for unit use... they were distributed from the same vault that issued pilots their "blood chits" (blood chit is a promise to pay an amount of money ($50,000 in gold I was told) for the helping with the safe return of a US airman shot down in enemy territory ...some time later I was sitting in an adult drinking establishment up country Thailand in 73, and noticed that a couple of the older gentlemen carried heavy ID bracelets made from gold...and rumors were that they could be used a link at a time to do the same thing... the ladies working in the establishment also carried baht bracelets with gold charms labeled with their weight in grams...their di di mao cash support
my next purchase was an elephant hide money belt, and in it I added a copy of my orders with security clearance on it, a new $50US bill, and when I got back to the PI, took a picture of my birth certificate and front page of my passport with a macro lens on slide film, to make a DIY microfiche of the data...
at the time cash money was high my E&E requirement...and even some 45+ years later, the idea still has some merit... though a little more than the $50 I could afford on an E5's salary
Les